Bolt lock for machine guns



Aug. 19, 1947.

J. L. LOCHHEAD BOLT LOCK FOR MACHINE GUNS Filed Oct. 30, 1942 2 Sheets-Sheet 1 JEN-m L- Luchhead- J. L. LOCHHEAD BOLT LOCK FOR MACHINE GUNS Filed 001:. 30; 1942 2 Sheets-Sheet 2 du'hn uputhhea 35 a/fnzlvzhwm Patented Aug. 19, 1947 IT ED STATES PAT JQFEFLE 2,425,749 I 3 1 4993? F013 John L. Lochhead, Springfield, Mass, assignor '--tothe United States of America, as represented -by the Seeretary of War An line? 09*93 9 0 92 1 erial this? 4 Claims. (01. 89-188) The invention described herein may be manniactured and'used by or for the Government for governmental purposes, without the payment 12 me of any royalty thereon.

This invention relates to improvements in bolt locks for machine-guns, such as disclosed in the United States Patent No. 1,628,226 to John Browning.

In aBrowning .gun provision for quick replace.-

ment of the barrel has made it expedient to finish the barrel vwith a wplani-iorm ibreeeh iace extendingflush to the .ehambenend to secure .the barrel in the barrel extension with the breech .faoe extending-into the :barrel extension slightly. The chamber is of less length than the cartridge, .80 that the head of the cartridge projects while held inthe T e-slot of the bolt. Adjustment lot the headspace.betweenitheabarrel and-bolt is a critical factor inoperation of these guns and properly the bolt at battery .doesnot press hard against {the headof the cartridge, butis stopped by the tips .of the Teslotwengagin'g the barrel, and the breech lock is depended on to fix-the .holt .at its forward limit in the barrel extension. Consequently in the prior gun the advance ioftbolt relative to the barrel extension can not equal the extent indicated in Figure 8 but may be greater in other guns; vor, the barrel extension of the Browning or other guns, using my invention maybe constructed .without any solid part to engage before and .stop the .bolt near or .at battery position, but enabling my lock to effect such stoppage at a time .when no shock will occur.

At times .a machine gun of the type disclosed in the above-mentioned patent will .fire out of battery due itO the barrel extension going into battery ahead .of :the bolt. When such a condiitionvoccurs, it isiimpossible for the breech lock to be. effective .andrtheboltand barrel extension will be dangerously unlocked at firing. .A suitable breech locking mechanism toiinsure positive relative tpositioningr-andzlocking together of the recoiling parts approaching battery is therefore desired. Y

liifhile undereertain-highrate of fire adjustments :in the known use of the prior gun, firing iseffectedwhilethe barrel extension isadvaneed slightlyrahead of thebolt advantage being taken of continuing .momentum of the bolt :t bring it into or near-batteryiwhile(explosion of the propellant is initiated) .without immediate gun-damage. or misfiring. Cl-his is undesirable =because recoil r-then (sometimes ioocurs before the :bolt is 'lpckeitmthe barreliextension, iwithvsevere shock or irexoessiye wear v.or breakage, ,modification of d under the act .of March '3, 1883, as

'2 kin ti operatin va u s o the reselling and .q n errecoi ne narlil liability o f cartrid e case rapture fmdnth rwise. My invention obviates the ij b l i$. 2i in ury while nermitting. pr per pner ette y firing.

instrnctionsfor nsing the Brownin un stress th fo equen adjustment of the headpa ei y v t me the nniscleaned .or after every en agemen ln nmcient 'headspace c s h h p toiam a a nst the prior Browning bolt lock, pre en in -full e t y of su l ok into the notch. stops movement of the barrel .extensionto fu batter p si on ac ompanied by l sh an on atleast iorsmay only prevent extractio of o. i ids? from the ammunition belt, or an extreme-ease lmeystopthe recoiline parts .iar enough rearward to prevent firing. Too much he adspaee has other manifestations .of faulty iqperation .aoqomnanied by liabilities, includin that-o ruptu e .01 the nalttridge vcase.

Whil my invention will not obvia e need i 2 ca efu main enance of proper headspace its 1 51 w li m n nuzeimpaired riuncz'tion and stoppage resulting-Iromlaekof eorrectheadspace.

A co din y i i an object of this invention. to produce an improved machine .gun action.

Another bject 0, this invention is to provide a b ea lock sfo positive ti i a vlocking .of the nrfiqqi ins member of a vma hin eu {El e specific nature of the invention as well a other objeqts and advantages thereof will dear annea rom a des rip n of a prefer e emb dime shonn initheaccompanvine winss in Whiq 'iFieis a partial side elevational .view .of a machine gun, partlyibrokenoawayoto show .the boltand; arrelfixtensiqn,i-nbattery.

Ei e. 4211 .a to elevationalview oiling. iwitht 9W Pa t al y broken away t h he :helt s 1 W- ,3 i tlsw nfirfi insecii n sh wing the he tendb eeq a ee e r si iqn- Fig. fl .is a uieyv imilar to Fig. .3 but gvith the bolt landlbreech ,loc battery position.

Fig. 5 is a cross, e anal -jrieyv on line 5 5 of Figl f f i ast- I s- Thi -.enlargesi ront .elevational View of t treaties? tFisH efiisa. l wsimil to Fi a eashow an earlier positionqf the'partsvvhenthe boltlis too'iaradvanjce'd'. -In Fig. 1 there is shown a partial longitudinal sectional view ofa machine gun such as disclosed i n witn sse vicwe i a tse h in U. S. Patent No. 1,628,226 to John M. Browning which embodies this invention. The gun as shown in Fig. 1 comprisesmainly a receiver I, a trunnion block 2 and a cover 3. Slidably mounted within the receiver I is a bolt L a barrel I3 and a barrel extension I4. A belt feed lever I5 is pivotally mounted on the cover 3. The belt feed lever l5 is a long flat member having ay narrow cam track l6, here shown as a slot (Fig.

2) in the center thereof which operates to impart a transverse movement to the lever I5 and hence to a belt feed slide or carrier 23 which is slidably mounted in the cover 3. The cam track defined by two oppositely disposed sides I? and I8 of the belt feed lever I5 which conform generally in shape to the cam track I5. of the belt feed lever I5 projects forwardly to form a rounded end 19. The end 19 fits'between two integral upwardly projecting lugs 24 and 25 provided on the belt feed slide 23. On the other end 20 of the belt feed lever I5 in the left side an outwardly projecting lug 2| is provided. A hole 22 is centrally provided in the projection 2| to mount the lever on the cover 3 by a bolt 26. The bolt 26 is inserted through either suitable hole 5 or 3 in the cover 3 and the bolt is secured to the cover 3 by a nut 21. A cotter pin 28 inserted in a suitable hole in the nut 2'1 and the bolt 26 prevents the nut 21 from unscrewing.

The cover 3 is pivotally mounted on the top of trunnion block 2 by a pin 4. When cover 3 is closed cam track It engages a stud 29 on bolt i so that belt feed lever I5 will be actuated by the reciprocating bolt to feed ammunition into the gun. The stud 29 is suitably secured in the center of an integral upwardly projecting lug 8 provided on the forward upper surface of the bolt 1. To aid in reducing friction between the cam track of the belt feed lever I5 and stud 23 a roller 30 may be suitably mounted on stud 29.

A rotary type of breech lock 3| is inserted in a suitable hole 38 in the barrel extension I4 approximately in the same location as the breech lock of conventional form. The lock 3| (Figs. 1, 6 and '7) is a cylindrical member having on each end similar coaxial longitudinally projecting portions. 32 semi-annular and of the same radius vertically as the body of the lock. The lower edges 33 of the portion 32 are finished in a diametrical plane of the lock member, which thus affords two fiat wiper or bearing surfaces 33 on the underside of each projection 32. A medial recess 34a is formed in the forward side of the look,

so that a planiform radial upper locking surface 34 is provided on the lock 3| extending from the axis of the lock to its periphery normal to the plane of the faces 33. A lower surface 34' slopes obliquely downward and forwardly at locked position of the lock, somewhat as shown in Fig. 6 and on the lower part of this surface 34' there is provided a small projecting lug 3'! to limit rotation of the lock 3| in unlocking movement. A shallow transverse cut across the top of the lock 3| forms a wide U-shaped flat bottomed notch 35 of less width than the recess 34a. Two projecting horn-shaped members 36 are thus provided on each side of the notch 35. These may be termed horns. They assist the boltinto battery position as will be presentlyv described. A notch .9 is provided on the underside of the bolt 1 to provide part of a locking surface Ill for the lock 3|. The notch 35 in the lock 3| allows a lock part 48 under the notch 35 to be rotated into the notch Bin the bolt! so that the locking sur- IB is...

One end 1 face 34 of the lock 3| engages the locking surface iii of the bolt 7.

On each side of the bolt 7 a recess II corresponding approximately in form to the horns 36 but of a greater radius, so as to normally clear the horns above and behind, as in Figures 4 and 5 is provided to permit the horns 36 to engage in these recesses and to assist the bolt into battery as will be explained. The forward sides of these recesses form continuations of the surface I5 of the recess 9, these continuations extending to a sufficient height to receive the forward planiform sides of the horns 36 thereagainst. A breech lock cam 33 is fixed on the bottom of thereceiver, arranged to guide the barrel extension and to actuate the breech lock 3|. This cam is of somewhat different configuration than the conventional breech lock cam because of the entirely different construction of the rotary lock 3|. The breech lock cam 39 is a U-shaped member (Fig. 5) arranged transversely of the receiver having upwardly projecting arms 40 and 4| close beside respective sides of the receiver, and on the interior surfaces of the arms there are formed respective inwardly projecting ribs 42. The ribs 42 engage suitable grooves provided in the barrel extension I4 to support and guide the barrel extension within the breech lock cam39 as the barrel extension I4 reciprocates therein. The upper rear corners 43 (Fig. 1) of the upwardly projecting arms 40 and 4| of the breech lock cam 33 are suitably rounded to provide a camming surface to engage one lower face 33 of each lock extension 32 when the barrel extension is returning to battery and impart a rotary motion to the lock 3| to lock the counterrecoiling bolt and barrel extension or the like of a machine gun as they move to battery position. The upper surfaces 44 (Fig. 1) of the arms 40 and 4| provide a suitable engaging surface for the bearing surfaces 33 when the lock is in the locked position. The cam 39 is secured to the bottom'plate of the receiver by the bolt 46.

The cycle of operation of the machine gun shown in Fig. 1 is similar to that disclosed in the previously mentioned patent to John M. Browning. The bolt I reciprocates in a straight line within the receiver after the discharge of each cartridge and effects feeding and loading of rounds by recoil and counterrecoil as well as ejecting shells as desired. Conventional trigger firing and recoil devices, operating substantially as in the prior gun mentioned, may be used.

In Fig. 1 and Fig. 4 recoiling parts of the gun are shown in the locked or battery position; that is, they are in position to permit safe firing of a cartridge. When the lock is in this position the surfaces 33 on the lock 3| rest on the surfaces 44 of the cam 39 and the locking surface 34 of the lock 3| engages the locking surface I 0 in the locking notch 9 provided on the underside of the bolt I. Also, the part 48 below the recess 35 engages in and fills the notch 9 to the rearward side of the latter, and the bolt may therefore be said to be locked to the barrel extension. As shown in its preferred form, the looking surface 34 of the lock 3| and the locking surface I 0 of the bolt 1 are formed at right angles to the lock surface 4410f the cam 39 so that they will engage each other in a plane normal to the paths-of the bolt and barrel extension. Such a locking surface affords a lockingfunction'of high effectiveness and utmost strength with a minimum of material and liability of t'looseness by 'wean'strain orplastic deformation. In addition,

5 when the bolt 1' is tiiererwam position shown iii s. 1 arm '4 the Horns -36 proyidea on the eiig'a'ge the forward "sides or the recesses died on tlfe bolt 1. V

Wh'n a cartridge is fired the force of the expiosion forces the r'coilin g member nainew, the bolt, Barrel extension and barrel to slide towards the rear, such members being held in locked r'ela tiofl by lock 3! re'co'ili'ng as a u nit therewith. Whfen the rear faces -33 of the lock 3! reach the iounizled corners 63 {of the cam 39, as the recon;- ii'ig members re driven rearwerdiy the reel; s1 tends to rotate around corner '43. Unlocking rotation of the lock is induced by pressure "of the bolt race T0 against d; race as. The pressure of the bolt in this way is developed byth'e greater impedance eirer'ee to the recoil of the barrel "exseason by the convehtiofial tuner springs, "aided iisually by a dash pot device. As the rearward movement erthe booming members continues complete unlocking is "effected by further rotation the lock by bolt i. This is ccomplished by the pressure exerted by the bolt at in on the lockirig s rface 34 or the "lock 3| 'well abo'ii'e the -iaxfsbf thelock 3-1 lth'erloy creating considerable average which facilitates rotation. or the look. It will lie-noted that the "face SQfe'xten'ds high on '38, arm a wipin action "or the bolt continues thereon '(at the "angle formed by the sanction er the bottom race of the bolt ahd the rower part er the'smrace l0) after the *part "as has 'movdfcleai' of the recess 9. After unlocking "mettle, assisted s in the prior by an accelerator 35 (which converts some of the energy of recoil of the barrel extension to acceleration of the bolt), travels rearwardly to the end of its stroke. During the latter part of this assisted movement of the bolt -in the Browning guns, as is known, the accelerator is moved by the barrel extension to a locking relation with the barrel extension by which the latter is held at full recoil position until return of the bolt over a i'fi'ajor part'bf its travel incounter'recoil.

In the unlocked position "as dotted in Figure 3 thewipenor bearing surfacesSS and the bottom of *i'ecss3-5 assume a vertical position and the projection "31 contacts the'botto'm of the bolt 1 thereby preventing further rearward rotation of the'lockisi. The recoil movement of the barrel and barrel 'extension is of comparativlyshort 'travelf-but-is sufi'icient to permit lock M "to be rotatdsiifliciently to fully unlock and 'assiiine 'th'ep'ositi'o'n shown in Fig. 3.

The bolt 1 is returned to battery position by an operating spring (not shown). approaches the position at which it is to be locke'dto the barrel extension, accelerator-" 35 is engaged byaprojecting portion [2 of the bolt I amen *moves the accelerator so as to release the barrel extensiori for return'by its recoil spring (not shown) and further aided by the bias of a spring (not shown) acting on the accelerator. This permits and also initially assists the barrel extension and barrel to go forward about the time the bolt is locked by the lock 3!. As is the common function of the prior bolt with the accelerator, and is also manifest with my invention, the relation between the bolt and accelerator is normally such that the bolt can not, at the time it strikes the accelerator move ahead of the barrel extension, because the accelerator forms an operating connection for the moment which fixes their relative position except when the accelerator is excessively worn, and under the latter condition the bolt may be slightly in As the bolt 8 advance of its proper position for looking to the barrel extension. After the accelerator has been completely operated and isin its forward position the parts normally move forwardly in a predetermined relation suitable for the function of my lock as above indicated and hereinafter ex"- plained. As the barrel and'barrel extension .pro' c'e'ed forward the rear edges of mm 39 Contact the lower surfaces 33 of lo'ck 3i and rotate lock 3i forwardly. Such rotation causes horns 35170 project upwardly and into recesses ll on-bolt 1. The bolt 1 meanwhile is continuing its forward motion. Upon engagement of the horns 36 in recesses H the cam 39 completes rotation of the lock and the counterrecoiling members continue forward. while rigidly joined by the lock into battery position, the lock 32 having been rotated into its fuly locked position as shown in Fig. 4. The locking surface 3 1 of lock 3 then fully engages locking surface 10 of bolt 1 and the bearing surfaces 133 of each -extension 32 both lie fully engaged on the "top of cam 3Z9. ther rotational movement er the lock is thus :prevented.

If, for "any reason the bolt tends to iriove ahead of the barrel extension at or immedi'ately after the function of the "accelerators, the extremities of the horns 36 will nevertheless havebeen raised in the lowerparts of there'cesses H "as in Figure '8, before the bottom or i 'ecss 35 reaches the level of the low'er f ace of the bolt, and tlrey will engage the reap-sides the -rece'Sse's l -l if the relative movement d's soj fa'r, well before the part "48 of tclock strike's th'e bottom of 'bolt,-' s'topI$irfga1i-y excessan rate of bolt counter-'- recon over move exit bf the "b'a'i r el e Xte-h'sioh. Thereafter, 1 corresponoin-g r i1 -m'eains for the barrel extensionfb'eing the more powerful, wi'll accelei ate the barrel extension and prevent any ratt-her relative advance of the bolt in i elation to tliebarrel extension. lock inely "then sanction-normally 'as before described. While the extrme condition of Figure -9 will hot'occiir in the current Brow-ning r gun lesser errors of positio'n of the bolt will b'e similarly*remedledbeforethe locks part' w' st hes the bolt. Construction of "the Br'ow'ni'ng gun so that the T-s lot 'lips are not depe'nded on t'o stop'advance of the bolt in-the barrel extension willeliminatebreakage of the li'p's now occurring from this c'a'use.

-In the functior-iingof the bolt and bairel-extension after operation of the accelerators, any tendency to -the bolt to become eSSentially'retard'ed will be o'vercoine "by the funetion "of the horns 36 against the angle at the lower parts of the face I'0 of i the recess l I so that the -bolt is pressed forwardly by' tl'ie horns -until the locking part "48 may enter the recess 9 snugly and the face 34 abuts the lower part of the locking surface II], as shown in Figure 4. Completion of the movement of the parts to battery is thus coordinated. This will prevent excessive headspace and attendant evils in many cases which have heretofore occurred in the Browning gun,

It may thus be readily seen that with this type of lock it is impossible for the bolt and barrel extension to go into battery in any position but the fully locked mutual position because of the projecting horns 36 which engage in the recesses I on the bolt regardless of how late or soon the bolt is returned to the accelerator on the closing stroke.

I claim:

1. In a machine gun having a receiver and a recoiling barrel, a barrel extension and a bolt reciprocable on the barrel extension; alocking assembly comprising a cylindrical lock body rotatably supported transversely in the barrel extension, a longitudinal projection on each end of said body having wiper parts located at opposite sides of the axis of the lock body, a fixed cam engaging said wiper parts and operative ,under movement of the barrel extension to engage the Wiper parts and rotate said cylindrical body, a central transverse notchbeing formed in said boltand a recess formed in the side of the bolt extended from the notch rearwardly and above the notch, the forward Walls of said notch and recess being coincident and shaped to form a locking surface, an extension on said body to extend above said notch to engage in said recess, the rear wall of said recess arranged to engage said extension as the bolt approaches battery position, whereby the engagement of said extension with said recess wall Will prevent the bolt going ahead of the keyed position of the bolt relative to the barrel extension, said cylindrical body having a lock part to engage and fill said notch and being rotatable by engagement of said cam against said wiper parts to engage said looking surfaces of the bolt and lock body and engagement of said lock part in said notch at the normal locked positions of the bolt and barrel extension.

2. In a machine gun having a receiver, a re coiling barrel and, barrel extension having a battery position therein, and a bolt slidable in and from the extension reciprocable in the receiver over a longer path than that of the extension and having a predetermined battery position, means to lock the bolt and said extension in a mutual firing relation during their counterrecoil in advance of and at said battery position, comprising a transverse U-shaped cam fixed in the receiver for reciprocation of the barrel extension therein, a generally cylindrical lock revolubly mounted in the barrel extension with its axis transverse to the cam, said lock having a medial recess to receive the bolt slidingly therethrough at one position of the lock, said bolt having a lock notch therein having front and rear faces arranged to align with the rear part of the look when the bolt is in said firing relation to the barrel extension, said lock having a rearward locking part to fit the said faces of said notch when the lock is rotated forwardly at said firing relation of the said extension and bolt, said lock having an axial extension having two Wiper faces in a common plane on opposite sides of the axis of the lock, said cam having an arm beside the barrel extension stopping near and below the axis of the lock and having a rear cam face positioned rearwardly of the battery position of the lock axis, said cam having also a horizontal upper face positioned to engage slidingly under both said Wiper faces of the lock over a limited extent of travel of the barrelv extension, the distance of the rearward wiper from the center of said lock being sufficient for it to engage the rear cam face when the lock is in open position in counterrecoil, whereby to be rotated to move on to said upper face, and to move the other wiper face commonly to and slid ably on said upper face. 7

3. The structure of claim 2 in which the rear cam face is vertical, a rounded face on the cam forming a junction of said cam faces, said wiper faces being in a common plane coincident with said upper face of the cam at locked position of the lock, said wiper faces being spaced apart more than the length of the chord of said rounded part of the cam.

4. The structure of claim 2, in which the said notch and locking part have top faces intermediately of the height of a vertical radius of the lock, said lock having a horn shaped part extended upwardly beside the bolt above the said locking part and said bolt having a safety recess in its side op on the bottom of the bolt to receive said horn shaped part and extending above the notch, the rear part of the safety recess being rearward of the notch curved forwardly from its lowermost part to its forward side, the safety recess and said notch having their forward sides formed by a single planiform vertical face, intersecting the bottom of the bolt, said lock part and horn shaped part also having a single continuous face to engage flat against the other planiform face at locked position of the parts. JOHN L. LOCI-IHEAD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 430,210 Maxim June 17, 1890 441,390 Browning Nov. 25, 1890 618,743 Silverman Jan. 31, 1899 698,107 De Knight Apr. 22, 1902 891,778 Mertens June 23, 1908 1,007,911 Bjorgum Nov. 7, 1911 1,709,162 Westervelt et al. Apr. 16, 1929 834,753 Reifgraber Oct. 30, 1906 639,421 Mauser Dec. 19, 1899 1,477,115 Gast Dec. 11, 1923 1,613,205 Soncini et a1 Jan. 4, 1927 1,453,439 Cedillo May 1, 1923 1,123,530 Heinemann Jan. 5, 1915 FOREIGN PATENTS Number Country Date,

700,629 Germany Dec. 24, 1940 692,244 Germany June 15, 1940 57,117 Germany June 23, 1891 

